Spindle Sander Drum Size Chooser
A sanding drum can only follow an inside curve if the drum is small enough to fit inside it. Enter the tightest curve in your project and the drums your machine can use to see which ones work.
Which drum fits your curve?
Enter the radius of the tightest inside curve, then the drum diameters your machine can use. The sizes shown are samples only.
Your workpiece
Drum diameters on your machine (leave unused boxes empty)
2 in drum
The tightest curve is a 1 in radius, so a drum can be at most 2 in across. The 2 in drum is the largest of yours that fits.
| Drum | Fits the curve? | Room to spare |
|---|---|---|
| 0.5 in | Fits | 0.75 in of radius |
| 0.75 in | Fits | 0.63 in of radius |
| 1 in | Fits | 0.5 in of radius |
| 1.5 in | Fits | 0.25 in of radius |
| 2 in | Fits | 0 in of radius |
| 3 in | Too large | Needs 0.5 in more radius |
Rule used: drum diameter must be no more than twice the smallest inside radius.
A drum that matches or is smaller than the curve will not flatten it. Outside (convex) edges and flat edges can be sanded with any drum. Check your machine’s manual for the drum and sleeve sizes it supports, and for table insert and sleeve height.
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2 in sanding sleeves on AmazonSanding sleeve sets on AmazonRadius is half the width of the curve. A curve that is 2 inches wide has a 1 inch radius.
The rule behind the chooser
A drum fits an inside curve when its diameter is no more than twice the curve’s radius. A curve with a 1 inch radius can take a drum up to 2 inches across; a tighter curve needs a smaller drum. The tool compares each drum you list against that limit and tells you the largest one that fits.
How to find the radius
Trace the curve on a card or the workpiece and find a circle or round object that matches it. Half of that round object’s width is the radius. If a project has several inside curves, use the tightest one, because that sets the limit for the whole piece. Outside curves and straight edges do not limit the drum.
Why a larger drum can be a good choice
When more than one drum fits, many woodworkers reach for the largest one that does, since it puts more abrasive against the edge and usually follows a gentle curve more smoothly. That is a rule of thumb, not a requirement. A smaller drum that also fits works too, and the finish depends on grit, feed speed and your hand control.
Enter your own drum sizes
Machines ship with different sets of drums or spindles, so the six boxes start with sample sizes you should replace with your own. Leave unused boxes empty. You can enter diameters in inches or millimeters. For exact sleeve dimensions and how they relate to your machine, use the sleeve finder and the sleeve converter.
What the chooser does not cover
It does not check whether a sleeve fits a particular drum, whether your table insert has an opening for the drum, or the sleeve height. Check the machine’s manual for supported sizes and for the sleeve and drum specifications before you buy abrasives.
Frequently asked questions
How do I choose the right spindle sander drum size?
Find the radius of the tightest inside curve, double it, and pick a drum no larger than that. This tool lists your drums against the limit and shows the largest that fits.
What is the largest drum for a curve with a 1 inch radius?
A drum up to 2 inches in diameter, because the drum diameter should not exceed twice the radius.
Do outside curves limit the drum size?
No. The size limit only applies to inside (concave) curves. Outside edges and straight edges can be sanded with any drum.
Should I always use the largest drum that fits?
Not always. It is a common rule of thumb for smoother results on gentle curves, but a smaller drum that fits works too. Choose based on the curve, the grit and the finish you want.
Does this tell me which sleeve to buy?
No. It only checks the drum diameter against the curve. Sleeve diameter, height and the drum or spindle that supports it must match your machine, so check the manual.
Are the Amazon links affiliate links?
Yes. They open Amazon search results and are tagged, so SpindleSander.net may earn a commission on qualifying purchases at no extra cost to you. A search result is not a compatibility check.